Vacuum chambers and various parts to be arranged in the chambers in plasma processing equipment typically for the production of semiconductors and liquid crystals mainly adopt aluminum alloys (metals). The aluminum alloys generally have an anodized aluminum film (anodic oxide film) formed through anodization on their surface, because the chambers and members are exposed to a corrosive gas such as chlorine-containing or bromine-containing gas and/or to plasma in an environment at room temperature to 200° C. or higher in a pretreatment process and/or in a production process. However, the anodic oxide film formed on the aluminum alloy may include some cracks, and the cracks may increase in number and/or grow in size in the high-temperature environment, and the corrosive gas invaded from the cracks may cause the corrosion of the base metal aluminum alloy. In particular, the anodic oxide film to be formed on the chambers and members in the processing equipment is formed to be relatively thick because the chambers and members are exposed to a plasma atmosphere and should have higher plasma resistance. However, such a relatively thick anodized oxide film is more susceptible to cracking and tends to fail to have sufficient corrosion resistance. To avoid this, Patent Literature (PTL) 1, for example, discloses an anodized aluminum-based metal material which bears an anodic oxide film and shows improved corrosion resistance, in which cracks in the anodic oxide film are filled with a burnt amorphous-silicon-containing substance formed by supplying an organic treatment solution to the anodic oxide film, which organic treatment solution is of an organic compound having a Si content of 10 atomic percent or more and having Si—O bonds in an organic solvent, and drying and firing the organic treatment solution.